242 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
in the course of work, I believe it will be better to centri- 
fuge the fixed catch for two minutes or so and then 
measure the volume, as carried out by Kofoid,* instead 
of taking the volume after settling for twenty-four hours. 
DIMENSIONS OF APSTEIN MEDIUM PLANKTON NET, 
q 
Diameter of opening, 14 cm. 
Area of opening, 155'3 cm. 
: ; at lower ring of conical head piece, 40 cm. 
Diameter of net 5 p ; 
Length of side of net, 100 cm. 
The corrected coefficients, wy, for the large Hensen net 
and the Apstein net are given by Lohmannf as 1°34 and 
1°39 respectively for a speed of pull one metre in two 
seconds. 
(at bottom where attached to filtering bucket, 6 cm. 
Length of side of conical head piece, 20 cm. 
| 
| 
1 
| 
* Kofoid. Loc. cit., p.254. 
+ Lohmann. Wissenschaft. Meeresuntersuch., N.F., Band VU, 
p. 17, Kiel, 1903, 
